Abstract:

Moderate physical training induced a decrease in arterial blood pressure in fish
oil-fed rats as compared to sunflower seed oil-fed rats [14]. The purpose of this
study was to determine if these changes were due to modifications of the left
ventricular function of the heart. Forty rats were fed a semi-purified diet
containing either 10% sunflower seed oil or 10% fish oil (EPAX 3000TG, Pronova).
Each dietary group was assigned to two sub-groups, one being constituted by
sedentary animals and the other by trained animals. Training was achieved by daily
running for 60 minutes at moderate intensity for three weeks. At the end of the
training period, the animals were sacrificed and their hearts were immediately
perfused according to the working mode. The phospholipid fatty acid composition and
parameters of the left ventricular function were determined. Feeding fish oil
markedly reduced the proportion of n-6 polyunsaturated fatty acids (PUFA, 18:2 n-6,
20:4 n-6, 22:4 n-6 and
22:5 n-6) in cardiac phospholipids. The n-6 PUFA were replaced by n-3 PUFA (mainly
docosahexaenoic acid). In sedentary animals, the fluid dynamic (aortic and coronary
flow, cardiac output) was not modified by the diet. The heart rate was reduced
(-10%) in n-3 PUFA-rich hearts. Physical training did not markedly alter the
polyunsaturated fatty acid profile of cardiac phospholipids. Conversely, it reduced
the heart rate, aortic flow and cardiac output (-11, -21 and ,
respectively) at
a similar extent in the two dietary groups. In a second set of experiments, the
training period was repeated in animals fed a commercially available diet (A103,
UAR) which simultaneously provided n-6 and n-3 fatty acids. In these dietary
conditions, neither the aortic flow nor the heart rate was decreased by physical
exercise. These results suggest that both n-6 and n-3 PUFA in the diet are necessary
to ensure a good cardiac adaptation to moderate physical training. Furthermore, the
fish oil-induced decrease in arterial blood pressure in trained animals was not
related to changes in cardiac contractility, but to a decrease in vascular
resistances. Moderate physical training + dietary n-3 PUFA might be used to prevent
hypertension and cardiovascular diseases.